Support Matrix and Operational Limits

This page explains what ActPlane can enforce today, what requires BPF-LSM, and what should be reviewed with actplane compile --explain before use.

Always start with:

actplane compile --explain --report-out docs/actplane-review.txt
actplane doctor

Use --json for CI:

actplane compile --json > actplane-compile-report.json

Effects

If several clauses match one event, ActPlane chooses the strongest effect:

kill > block > notify

Operation Coverage

Pattern Support

Hook Profiles

ActPlane loads the hook classes needed by the compiled policy. Some runtime deltas can only be accepted later if the relevant hook and matcher classes were reserved when the engine loaded.

Use the full profile for long-running MCP/watch sessions that will accept child domain deltas whose final policy is not known at startup.

BPF-LSM vs Tracepoint Mode

Tracepoint-only mode is still useful for observation, corrective feedback, and many harness-level policies. Use BPF-LSM for hard security boundaries.

Data-Flow Semantics

Labels propagate across:

• fork and exec lineage
• file reads and writes
• supported network receive/send paths
• supported fd duplication and IPC paths in advanced profiles

This is conservative. A process that reads a small secret value can taint later files or processes even if some later output does not literally contain the secret. That over-tainting is intentional: ActPlane favors preserving provenance over silently missing a derived flow.

Temporal Gates

after exec G is latching: once it has happened in a lineage, it remains true.

Use since for freshness:

after exec "**/pytest" exits 0 since write "src/**"

This means the gate is valid only if pytest exited 0 after the latest write to src/**. Any later matching write makes the gate stale.

Runtime Deltas

Runtime deltas are append-only policy changes applied to a running engine:

actplane control delta add --target-id <domain-id> --delta policy-delta.dsl

Allowed delta shape:

• add local bindings
• add labels
• add gates
• add restrictions
• narrow scope
• create child domains within delegated authority

Rejected delta shape:

• remove inherited rules
• weaken parent policy
• widen scope
• remove labels or gates
• mutate an existing rule definition
• introduce hook or matcher classes not reserved at load time

If configured, runtime-delta admission can require metadata:

actplane control delta add \
  --target-id <domain-id> \
  --delta policy-delta.dsl \
  --approved-by alice \
  --approval-ref REVIEW-123 \
  --generated-by codex

The current admission gate is deterministic local metadata checking. It is not a cryptographic signature or external ticket-system verifier.

Attach Limits

actplane attach --pid <pid> is post-hoc:

sudo -E actplane attach --pid <pid>

It protects future events from the attached process tree, but it does not reconstruct:

• prior file reads or writes
• prior network flows
• prior labels
• prior temporal gates
• prior ancestry outside the attached tree

For strict history from process start, use:

sudo -E actplane run -- <cmd>

or project MCP auto-attach:

actplane init --with-mcp

Recommended Rollout

1. Generate or choose a policy.

   actplane init --list-templates
   actplane init --template no-git-branch --out actplane.yaml

2. Review support and limits.

   actplane compile --explain --report-out docs/actplane-review.txt
   actplane doctor

3. Start with notify or a narrow kill policy when possible.

4. Move to block only after compile --explain confirms BPF-LSM support for the relevant clauses.

5. For long-running parent/child sessions, reserve the hook profile needed by expected child deltas before the engine starts.

6. Keep .actplane/last-violation.txt with incident artifacts when a policy fires; it is the human-readable record of the corrective reason.